Several embodiments are known in the state of the art which are applied to detect defects in yarn bobbins.
Japanese patent application 62-62938 and U.S. Pat. No. 5,138,151 disclose methods for detecting based on sensors for acquiring image by line by line reading, provided to give rise to a station embedded in a line to transfer bobbins toward a storage or service area.
This prior art methods have the main drawback that for localizing a defect it requires two or three acquisitions of the image sensor, its use meaning in addition limitations as for the bobbin colour and/or material, which make the general use of this method difficult which is mainly useful for direct reflection bobbins. In addition, as this kind of sensors only read one line, the encompassed field is then very restricted and the shots have to be performed at points very near to achieve effective results.
On the other hand, Japanese patent application 134105 and U.S. Pat. No. 5,359,408 disclose devices for inspecting spinning bobbins comprising a matrix type camera image acquisition means, the later of these background disclosing arrangements applied for detecting different defects with the use of several types of lighting sources such as ultraviolet rays, fluorescent or other.
However in said prior art patents the possibility is not contemplated to perform a complete scanning of all the bobbin surfaces, carrying out an inspection of multiple and different defects, which occurs in some cases twice or more times and by means of one or two stations embedded in a conveyor line of recently produced bobbins with the peculiarity that it is adaptable to different bobbin sizes and regardless the bobbin colour and material characteristics be.
There are not either disclosed in the state of the art the series of arrangements relative to image acquisition sensors and lighting sources this invention proposes and which namely provides with an effect of field depth such it allows to accurately focus the defects at each scanned sector which significantly facilitates their identification.